KR102487276B1 - Inkjet printing method and display device manufacturing method using the inkjet printing method - Google Patents

Abstract

setting a first area to be printed at a constant print density in the area to be printed; setting a second area to be printed with a printing density that varies depending on the location, as an area located at an edge of the print target area relative to the first area; generating control data for a plurality of nozzles provided in an inkjet head to print the first area and the second area; and driving the inkjet head according to the control data.

Description

Inkjet printing method and display device manufacturing method using the same {Inkjet printing method and display device manufacturing method using the inkjet printing method}

The present invention relates to a method of forming an inkjet-based thin film and a method of manufacturing a display device using the same.

The inkjet printing method is a non-contact printing technology and is widely used in various fields.

In inkjet printing, a plurality of inkjet heads are arranged on an area to be printed, and droplets of a predetermined interval and size are ejected onto the printing area through nozzles of the inkjet heads. The size and spacing of droplets are determined according to the area to be printed or the target film thickness.

The liquid droplet sprayed onto the printing area is flattened by its own weight and spreads like a liquid to form a film thickness. At this time, droplets injected near the edge of the print area spread like a liquid even in the direction toward the outside of the print area, and the thickness becomes non-uniform near the edge of the print area, and the boundary shape tends to become unclear.

The present invention provides an inkjet printing method with good film thickness distribution control.

According to one aspect of the present invention, setting a first area to be printed with a constant print density with respect to the area to be printed; setting a second area to be printed with a printing density that varies depending on the location, as an area located at an edge of the print target area relative to the first area; generating control data for a plurality of nozzles provided in an inkjet head to print the first area and the second area; and driving the inkjet head according to the control data.

A printing density of the second area may be lower than a printing density of the first area.

A printing density of the second area may decrease toward an edge of the printing target area.

The control data controls the interval or volume of droplets to be ejected in the unit area when the first area and the second area are divided into a plurality of unit areas facing the plurality of nozzles provided in the inkjet head. It may be data for

The generating of the control data may include setting a basic driving voltage that satisfies a predetermined basic discharge amount tolerance range for each of a plurality of nozzles provided in the inkjet head.

In the generating of the control data, basic driving voltages set for each of the plurality of nozzles are arranged in a row in a first direction in which the plurality of nozzles are arranged, and the inkjet head moves relative to the print target area. Control data for printing the first area may be generated in a matrix form in which the rows are repeated along the second direction.

The generating of the control data may further include selecting a printing density variable method for the second area.

The printing density variable method may be a droplet volume control type, a printing interval control type, or a combination thereof.

The generating of the control data may further include determining a ratio of droplets to be ejected to a plurality of unit areas of the second area to the basic discharge amount when a droplet volume control type is selected as the variable printing density method. can do.

The generating of the control data may include a matrix form obtained by multiplying the ratio determined for each of a plurality of unit areas of the second area by a basic driving voltage determined for each of a plurality of nozzles facing the plurality of unit areas. As the data, control data for printing the second area may be generated.

The generating of the control data may include: determining a ratio of an interval between droplets to be injected in the second area to an interval between droplets to be sprayed in the first area when a print spacing adjustable type is selected as the variable printing density method; may further include.

The generating of the control data may include forming bitmap data in which a position at which a liquid droplet is to be ejected is set to 1 and a position at which it is not to be ejected is set to 0 for a plurality of unit areas of the second area, according to the interval ratio. ; may be further included.

The generating of the control data may include multiplying the bitmap data determined for each of a plurality of unit areas of the second area by a basic driving voltage determined for each of a plurality of nozzles facing the plurality of unit areas. Control data for the second area may be generated as data in a matrix form.

The generating of the control data may include, when a mixed type is selected as the variable printing density method, determining a ratio of liquid droplets to be ejected to the plurality of unit areas of the second area to the basic discharge amount; and determining an interval ratio between droplets to be injected into the second region with respect to an interval between droplets to be injected into the first region.

The generating of the control data may include forming bitmap data in which a location where a liquid droplet is to be ejected is set to 1 and a position where a droplet is not to be ejected is set to 0 for the plurality of unit areas of the second area according to the interval ratio; may further include.

The generating of the control data may include the bitmap data determined respectively for a plurality of unit regions of the second region, the ratio determined respectively for a plurality of unit regions of the second region, and the plurality of Control data for printing the second area may be generated as data in a matrix form obtained by multiplying unit areas by a predetermined basic driving voltage for each of a plurality of nozzles facing each other.

Also, according to one type, forming a display substrate on which display elements are arrayed; and encapsulating the display substrate using an inkjet printing method, wherein the inkjet printing method includes setting a first area to be printed at a constant printing density with respect to an area to be printed; setting a second area to be printed at a print density lower than that of the first area, as an area located at an edge of the print target area relative to the first area; generating control data for a plurality of nozzles provided in an inkjet head to print the first area and the second area; and driving an inkjet head according to the control data.

The display elements may be organic light emitting elements.

Further, according to one type, forming a first substrate on which pixel circuits and pixel electrodes for controlling a plurality of display areas are formed; and forming a first alignment layer on the first substrate using an inkjet printing method, wherein the inkjet printing method includes setting a first area to be printed at a constant print density with respect to an area to be printed; setting a second area to be printed at a print density lower than that of the first area, as an area located at an edge of the print target area relative to the first area; generating control data for a plurality of nozzles provided in an inkjet head to print the first area and the second area; and driving an inkjet head according to the control data.

The display device manufacturing method may include forming a second alignment layer on a second substrate by using the inkjet printing method; and forming a liquid crystal layer between the first substrate and the second substrate.

According to the inkjet printing method described above, it is possible to form a thin film with good film thickness distribution near the edge of the region to be printed.

Since the above-described inkjet printing method does not use an additional structure for film thickness control, the process is easy.

The aforementioned inkjet printing method can be applied to various fields, such as an alignment layer of a liquid crystal display device or an encapsulation layer of an organic light emitting display device.

1 is a flowchart schematically illustrating an inkjet printing method according to an embodiment of the present invention.
FIG. 2 is a flowchart schematically illustrating a step of generating control data in the inkjet printing method of FIG. 1 .
3 shows an example of data in which a basic driving voltage is set for each of a plurality of nozzles provided in an inkjet head.
FIG. 4 shows an example of generating control data for the first region from the basic driving voltage data illustrated in FIG. 3 .
FIG. 5 shows an example in which an inkjet head is driven according to the control data of FIG. 4 and a droplet is jetted to a first area.
6 is a flowchart illustrating in detail the step of generating control data for the second area.
FIG. 7 is a graph showing a variable print density profile to be applied to control data generation for a second region in the flowchart of FIG. 6 as an example.
FIG. 8 is adjustment data exemplarily showing ratios of droplets to be ejected to unit areas of the second area with respect to the basic discharge amount when the droplet volume control type is selected as the printing density variable method in the flow chart of FIG. 6 .
FIG. 9 shows an example in which control data for the second region is generated from the basic driving voltage data set in FIG. 3 and the adjustment data in FIG. 8 .
FIG. 10 shows an example in which an inkjet head is driven according to the control data of FIG. 9 and droplets are jetted to a second area.
FIG. 11 is bitmap data showing whether or not droplets are ejected for a unit area of a second area when a printing interval adjusting type is selected as a printing density variable method in the flowchart of FIG. 6 .
FIG. 12 shows an example of generating control data for the second region from the basic driving voltage data set in FIG. 3 and the bitmap data of FIG. 11 .
FIG. 13 shows an example in which the inkjet head is driven according to the control data of FIG. 12 and droplets are ejected in the second area.
14 and 15 are adjustment data and second exemplarily showing ratios of liquid droplets to be ejected to unit areas of the second area to the basic discharge amount, respectively, when the mixed type is selected as the printing density variable method in the flow chart of FIG. 6 . It is bitmap data indicating whether droplets are sprayed for the unit area of the area.
FIG. 16 shows an example in which control data for the second region is generated from basic driving voltage data set in FIG. 3 , adjustment data in FIG. 14 , and bitmap data in FIG. 15 .
FIG. 17 shows an example in which an inkjet head is driven according to the control data of FIG. 16 and a droplet is jetted to a second area.
18 is a graph showing a comparison of film thickness distribution in the vicinity of the edge of a print area formed by an inkjet printing method according to an embodiment with that of a comparative example.
19 is a cross-sectional view showing an example of a display device to which an inkjet printing method according to an embodiment is applied.
20 is a cross-sectional view showing another example of a display device to which an inkjet printing method according to an embodiment is applied.

Since the present invention can apply various transformations and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. Effects and features of the present invention, and methods for achieving them will become clear with reference to the embodiments described later in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various forms.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, and when describing with reference to the drawings, the same or corresponding components are assigned the same reference numerals, and overlapping descriptions thereof will be omitted. .

In the following embodiments, terms such as first and second are used for the purpose of distinguishing one component from another component without limiting meaning.

In the following examples, expressions in the singular number include plural expressions unless the context clearly dictates otherwise.

In the following embodiments, terms such as include or have mean that features or components described in the specification exist, and do not preclude the possibility that one or more other features or components may be added.

In the following embodiments, when a part such as a film, region, component, etc. is said to be on or on another part, not only when it is directly above the other part, but also when another film, region, component, etc. is interposed therebetween. Including if there is

In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, since the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, the present invention is not necessarily limited to the illustrated bar.

1 is a flowchart schematically illustrating an inkjet printing method according to an embodiment of the present invention.

In the inkjet printing method according to the embodiment, in order to improve the film thickness distribution or boundary shape near the edge of the print target area, an area with a constant print density and an area with a variable print density are set, and the set print density is implemented by inkjet printing. drive the head

Here, the print density means the amount of droplets ejected per unit area of the area to be printed during inkjet printing, and is determined by the volume of each droplet and the distance between droplets. The print density may differ from the film thickness distribution finally realized by inkjet printing.

Referring to FIG. 1 , the inkjet printing method includes the steps of setting a first area to be printed with a constant print density for an area to be printed (S100), and setting a second area to be printed with a print density that varies depending on the position (S100). S200).

The second area is an area located relatively close to the edge of the area to be printed compared to the first area. When setting the second region, details such as the location and area of the second region may be determined, and for this purpose, for example, the film thickness to be formed in the first region may be considered. The print density of the second area is set lower than that of the first area. The print density of the second area may vary depending on the location, and may decrease toward the edge, for example. The step of setting the first area (S100) and the step of setting the second area (S200) are not limited to the order, and it does not matter which step is performed first or simultaneously.

When the first area and the second area are set, control data for a plurality of nozzles provided in the inkjet head is generated to print the first area and the second area (S300). The control data may be data for controlling an interval or volume of droplets to be ejected in each unit area when the area to be printed is divided into a plurality of unit areas facing the plurality of nozzles of the inkjet head. In other words, for each of a plurality of unit areas in which a plurality of nozzles face the printing target area according to the relative movement of the inkjet head with respect to the printing target area, control information on whether droplets are ejected or driving voltage is provided. . Control data may be generated in matrix form.

The process of setting the first area (S100), setting the second area (S200), and generating control data (S300) is not limited to the order shown in the flowchart. For example, after setting the first area and generating control data for the first area, setting the second area and generating control data for the second area may be performed, or the order may be reversed. may be

When the control data is generated, the inkjet head is driven according to the control data (S400). When the inkjet head is driven, control data in the form of a matrix in which the direction in which the inkjet head travels is a row and the direction in which a plurality of nozzles are arranged is a column is used. The control data includes information related to droplets to be ejected in each of a plurality of unit areas of the printing target area, and information on which unit area of the printing target area is encountered by each nozzle is a stage for relative movement of the inkjet head. Provided by encoder data. The inkjet head jets droplets to the area to be printed according to control data interlocked with stage encoder data.

FIG. 2 is a flowchart schematically illustrating a step of generating control data in the inkjet printing method of FIG. 1 .

The control data generation step (S300) includes setting a basic driving voltage that satisfies a predetermined basic discharge amount tolerance range for each of a plurality of nozzles (S310), generating control data for the first region (S330), A step of generating control data for the 2 regions (S350) may be included.

The plurality of nozzles provided in the inkjet head are driven on/off by individually provided actuators, for example, piezoelectric elements, and the driving voltage for ejecting the same volume of liquid droplets may be different for each nozzle according to manufacturing tolerances. The step of setting the basic driving voltage (S310) is a step of checking the basic driving voltage providing the basic discharge amount for each nozzle in consideration of this. The basic driving voltage set in this step is used as a reference value for changing the droplet volume when generating control data for the first area and control data for the second area.

After the basic driving voltage is set, control data generation of the first region (S330) and control data generation of the second region (S350) are not limited in order, and any step may be preceded.

3 shows an example of data in which a basic driving voltage is set for each of a plurality of nozzles (N1, N2, N3, N4, N5, and N6) provided in the inkjet head 100.

The basic driving voltage data V may be expressed as a set of driving voltage values at which each of the plurality of nozzles N1 , N2 , N3 , N4 , N5 , and N6 of the inkjet head 100 ejects a predetermined basic discharge amount. As illustrated, the basic driving voltage data V may be provided in the form of a matrix of one row indicated along a direction in which the plurality of nozzles N1 , N2 , N3 , N4 , N5 , and N6 are arranged. Each voltage value included in the basic driving voltage data (V) does not mean a value that completely matches the basic discharge amount of each nozzle, and may be set to a value that satisfies the basic discharge amount tolerance range determined according to process conditions.

FIG. 4 shows an example in which control data CD1 for the first region is generated from the basic driving voltage data V illustrated in FIG. 3 , and FIG. 5 shows an inkjet head ( 100) is driven and the droplet LD is sprayed on the first area.

In FIG. 4 , D1 indicates a direction in which the plurality of nozzles N1 , N2 , N3 , N4 , N5 , and N6 are arranged, and D2 indicates a relative movement direction of the inkjet head 100 . The control data CD1 is in the form of a matrix including control information about unit areas of the first area that the plurality of nozzles N1, N2, N3, N4, N5, and N6 face while moving along the D2 direction. can be created Since the first area has a constant printing density, the control data CD1 for the first area has a matrix form in which rows of the basic driving voltage data V set in FIG. 3 are repeatedly arranged along the second direction D2. can have

The inkjet head 100 ejects the droplets LD to the first area R1 of the area to be printed according to the generated control data CD1. Each of the nozzles N1, N2, N3, N4, N5, and N6 is uniformly applied with a driving voltage of a value determined as a basic driving voltage, and sprays droplets LD while moving along the second direction D2. The distance between the droplets LD is determined according to the relative movement speed of the inkjet head 100 with respect to the area to be printed and the ejection frequency of each of the nozzles N1, N2, N3, N4, N5, and N6. The control data CD1 is data for uniformly ejecting the distance between the droplets LD and the volume of the droplets LD, and each nozzle N1, N2, N3, N4, N5, and N6 is a constant The droplet LD is ejected at the ejection frequency. Accordingly, as shown in FIG. 5 , droplets LD are sprayed to the first region R1 at regular sizes and intervals.

6 is a flowchart illustrating in detail the step of generating control data for the second region (S350).

To generate control data for the second area, first, a printing density variable method for the second area is selected (S355). As the printing density variable method, a droplet volume control type 361, a printing interval control type 371, and a mixed type 381 may be selected.

A print density profile to be formed in the second region may be set together with the selection of the variable print density method or before or after the variable print density method is selected.

Referring to FIG. 7 , the second area R2 is divided into a 2-1st area R2_1, a 2_2nd area R2_2, and a 2_3rd area R2_3, and the printing density of each area can be set. In the graph, the printing density of the first region R1 is indicated as 1.

The area indicated by DS is a dead space, that is, a position where a thin film by inkjet printing is not formed, and ED indicates the edge of the area to be printed.

Control data for the second area is generated according to the selected print density variable method and the print density profile to be implemented.

Referring to FIGS. 8 to 10 together, a process of the case where the droplet volume control type is selected in the flowchart of FIG. 6 (S361) will be reviewed.

FIG. 8 is adjustment data VR1 exemplarily showing the ratio of the basic discharge amount of droplets to be ejected to unit areas of the second area when the droplet volume control type is selected as the print density variable method in the flow chart of FIG. 6; FIG. 9 shows an example of generating the control data CD2_1 for the second area from the basic driving voltage data V set in FIG. 3 and the adjustment data VR1 in FIG. 8, and FIG. 10 shows the control data of FIG. 9 An example in which the inkjet head 100 is driven according to (CD2_1) and the droplet LD is jetted to the second region R2 is shown.

When the droplet volume control type is selected (S361), a ratio of the basic discharge amount of droplets to be ejected to the plurality of unit areas of the second area is set (S363).

Here, the basic discharge amount means the amount of droplets ejected by the basic driving voltage set in FIG. 3 . The ratio is set to a value for each of a plurality of unit areas so as to implement the print density profile illustrated in FIG. 7, and as shown in FIG. Matrix-type adjustment data VR1 defined in the second direction D2 may be set. As described above, the first direction D1 and the second direction D2 represent directions in which the plurality of nozzles of the inkjet head are arranged and relative movement directions of the inkjet head with respect to the area to be printed, respectively.

Next, matrix-type control data is formed by multiplying the ratio determined for each unit area by the basic driving voltage for each nozzle (S365).

Referring to FIG. 9 , the control data CD2_1 has a matrix form in which row and column directions are set in the first direction D1 and the second direction D2, and each position (i, The value in j) is determined as follows.

{CD2_1} _ij ={VR1} _ij *{V} _j

The inkjet head 100 ejects the droplets LD to the first area R2 of the area to be printed according to the control data CD1. When the inkjet head 100 moves along the second direction D2 and encounters a plurality of unit areas, each nozzle N1, N2, N3, N4, N5, and N6 has control data set for the corresponding area ( The driving voltage included in CD2_1) is applied, and droplets are ejected accordingly. While moving along the second direction D2, the plurality of nozzles N1, N2, N3, N4, N5, and N6 eject droplets at a constant discharge frequency.

Accordingly, as shown in FIG. 10 , in the second region R2, the droplet LD is formed in such a manner that the interval between the droplets LD is constant and the volume of the droplet LD gradually decreases toward the edge ED. is sprayed Here, the interval between droplets LD means the distance between centers of adjacent droplets LD. The volume of the droplet LD gradually decreases toward the 2_1st region R2_1, 2_2nd region R2_2, and 2_3rd region R2_3.

Referring to FIGS. 11 to 13 together, a process in the case where the printing interval adjustment type is selected in the flowchart of FIG. 6 (S371) will be described.

FIG. 11 is bitmap data BM1 showing whether or not droplets are ejected for the unit area of the second area when the printing interval adjustment type is selected as the printing density variable method in the flow chart of FIG. 6, and FIG. An example of generating the control data CD2_2 for the second area from the basic driving voltage data V and the bitmap data BM1 of FIG. 11 is shown, and FIG. 13 shows an inkjet control data CD2_2 of FIG. An example in which the head 100 is driven and the droplet LD is sprayed to the second region R2 is shown.

When the print spacing adjustable type is selected as the variable printing density method (S371), the ratio of the spacing between the droplets to be sprayed to the second area to the spacing between the droplets to be sprayed to the first area is set (S373). That is, when the interval between droplets in the first area having a constant printing density is 1, the interval between droplets in the second area may be determined as a variable number depending on the position. Such an interval may be determined in a form capable of implementing a print density profile set as shown in FIG. 7 , for example.

Next, bitmap data indicating whether droplets are ejected is formed in the plurality of unit areas of the second area according to the predetermined interval ratio (S375). The bit value may set an area where the droplet is to be ejected as 1 and an area where the droplet is not ejected as 0. Bit-trap data BM1 in a matrix form as shown in FIG. 11 is formed.

Next, matrix-type control data CD2_2 is generated by multiplying the bitmap data determined for unit areas of the second area by the basic driving voltage for each nozzle (S377).

Referring to FIG. 12, the control data CD2_2 has a matrix form in which row and column directions are set in the first direction D1 and the second direction D2, and each position (i, The value in j) is determined as follows.

{CD2_2} _ij ={BM1} _ij *{V} _j

The inkjet head 100 ejects the droplets LD to the second area R2 of the area to be printed according to the control data CD2_2. When the inkjet head 100 moves along the second direction D2 and encounters a plurality of unit areas, each nozzle N1, N2, N3, N4, N5, and N6 has control data set for the corresponding area ( The driving voltage included in CD2_2) is applied, and droplets are ejected accordingly. While moving along the second direction D2, the plurality of nozzles N1, N2, N3, N4, N5, and N6 eject droplets at different discharge frequencies. For example, the nozzles N1 and N2 discharge droplets at a discharge frequency of f ₀ /2 when f ₀ is the discharge frequency when printing according to the control data CD1 and CD2_1 of FIG. 5 or 9 . spray The nozzles N3 and N4 eject droplets at a discharge frequency of f ₀ /3, and the nozzles N5 and N6 eject droplets at a discharge frequency of f ₀ /4.

Accordingly, as shown in FIG. 13, the volume of the droplets LD is constant in the second region R2, and the distance between the droplets LD gradually decreases toward the edge ED. is sprayed That is, in the order of the 2_1st area R2_1, 2_2nd area R2_2, and 2_3rd area R2_3 approaching the edge ED, the interval between the droplets LD gradually increases.

Referring to FIGS. 14 to 16 together, a process in the case where the mixed type is selected in the flowchart of FIG. 6 (S381) will be reviewed.

14 and 15 show adjustment data (VR2) exemplarily showing ratios of liquid droplets to be ejected in unit areas of the second area to the basic discharge amount when the mixed type is selected as the printing density variable method in the flow chart of FIG. 6 . and bitmap data BM2 indicating whether droplets are ejected for the unit area of the second area. FIG. 16 is an example of generating control data CD2_3 for the second area from the basic driving voltage data V set in FIG. 3 , the adjustment data VR2 in FIG. 14 , and the bitmap data BM2 in FIG. 15 . FIG. 17 shows an example in which the inkjet head 100 is driven according to the control data CD2_3 of FIG. 16 and the droplet LD is jetted to the second region R2.

When the mixed type is selected as the printing density variable method (S381), the ratio of the basic discharge amount of droplets to be ejected to the unit areas of the second area is set (S383).

The basic discharge amount means the amount of droplets ejected by the basic driving voltage (V) set in FIG. 3 . The ratio data for the basic discharge amount is set as a value for each of a plurality of unit areas, and as shown in FIG. 14, a matrix in which row and column directions are set in the first direction D1 and the second direction D2 Adjustment data VR2 of the shape is set.

In addition, a ratio of the interval between droplets to be injected to the second region to the interval between droplets to be injected to the first region is set (S385). When the interval between droplets in the first area having a constant printing density is 1, the interval between droplets in the second area may be determined as a variable number depending on the position.

The order of S383 and S385 is not limited to the above description and may be performed simultaneously or the order may be reversed.

The ratio data for the basic discharge amount and the interval data of droplets to be ejected in the second area may be determined in a form capable of realizing a set print density profile, for example, as shown in FIG. 7 .

Next, bitmap data indicating whether droplets are ejected is formed in the plurality of unit areas of the second area according to the predetermined interval ratio (S387). The bit value may set an area where the droplet is to be ejected as 1 and an area where the droplet is not ejected as 0. Bit-trap data BM2 in a matrix form as shown in FIG. 15 is formed.

Next, matrix-type control data CD2_3 is generated by multiplying the bitmap data determined for unit areas of the second area, the ratio of the basic discharge amount of droplets to be ejected to the unit areas, and the basic driving voltage for each nozzle ( S389)

Referring to FIG. 16, the control data CD2_3 has a matrix form in which row and column directions are set in the first direction D1 and the second direction D2, and each position (i, The value in j) is determined as follows.

{CD2_3} _ij ={VR2} _ij *{BM2} _ij *{V} _j

The inkjet head 100 ejects the droplet LD to the second area R2 of the area to be printed according to the control data CD2_3. When the inkjet head 100 moves along the second direction D2 and encounters a plurality of unit areas, each nozzle N1, N2, N3, N4, N5, and N6 has control data set for the corresponding area ( The driving voltage included in CD2_3) is applied and the droplet LD is ejected accordingly. When the value of the control data (CD2_3) of the unit area facing each of the nozzles (N1, N2, N3, N4, N5, and N6) is 0, this is a position where the droplet LD is not ejected. To this end, each nozzle (N1) , N2, N3, N4, N5, N6) may be adjusted. While moving along the second direction D2 , the plurality of nozzles N1 , N2 , N3 , N4 , N5 , and N6 may eject the liquid droplets LD at different discharge frequencies. When the discharge frequency at the time of printing according to the control data (CD1) (CD2_1) of FIG. 5 or FIG. 9 is f ₀ , the nozzles N1, N2, N3, and N4 drop droplets at a discharge frequency of f ₀ /2 ( LD), and the nozzles N5 and N6 may eject the liquid droplet LD at an ejection frequency of f ₀ .

Accordingly, as shown in FIG. 17, in the second region R2, the volume of the droplet LD and the interval between the droplets LD are the 2_1 region R2_1, the 2_2 region R2_2, and the 2_3 region R2_3. ), the droplets LD are ejected in different shapes. As the 2_1st area R2_1, 2_2nd area R2_2, and 2_3rd area R2_3, that is, closer to the edge ED, the printing density decreases. For example, in the 2_1 region R2_1, droplets LD having the same volume as the droplet LD injected in the first region R1 illustrated in FIG. 5 are disposed in a form in which the interval between the droplets LD is doubled. and has a lower printing density than that of the first region R1. In the 2_2 region R2_2, droplets LD having a smaller volume than the droplets LD injected in the 2_1 region R2_1 are injected at the same interval as the droplet LD in the 2_1 region R2_1. It has a lower printing density than the 2_1 area (R2_1). In the 2_3 region R2_3, droplets LD having a smaller volume than the droplets LD injected in the 2_2 region R2_2 are injected at intervals smaller than the intervals between the droplets LD in the 2_2 region R2_2. It has a lower printing density than the 2_2 region R2_2.

The above descriptions have exemplarily suggested various methods of varying the print density near the edge of the region to be printed, and specific numerical values related to the number of regions, driving voltage, ratio, interval, etc. may be variously changed.

18 is a graph showing a comparison of film thickness distribution in the vicinity of the edge of a print area formed by an inkjet printing method according to an embodiment with that of a comparative example.

The comparative example shows the film thickness formed by the inkjet printing method in the case where variable printing density is not applied.

In inkjet printing, usually, the film thickness gradually decreases toward the edge (ED) of the area to be printed, and then a region of increased thickness, called coffee stain, appears near the edge (ED) due to the spreadability of the solution. In the embodiment, a coffee stain effect is reduced by setting a predetermined area near the edge ED as a variable printing density area and spraying droplets of a controlled size and spacing according to the above-described method. Compared to the comparative example, it can be seen that the width of the area where the film thickness increases near the edge ED or the area where the film thickness decreases toward the edge is reduced.

The inkjet printing method described above can improve the quality of the film thickness near the edge of the region to be printed, and can be utilized in various fields. For example, it can be used to form an alignment layer of a liquid crystal display device or an encapsulation layer of an organic light emitting display device.

19 is a cross-sectional view showing an example of a display device to which an inkjet printing method according to an embodiment is applied.

The display device 500 is an organic light emitting display device, and includes a display substrate 570 on which organic light emitting diodes (OLEDs) are arrayed, and an encapsulation film EC encapsulating the display substrate 570 .

The display substrate 570 includes a substrate 510, a pixel circuit 520 formed on the substrate 510, an insulating layer 530 covering the pixel circuit 520, an organic light emitting diode (OLED), and a pixel defining layer 540. include The pixel circuit 520 may include a thin film transistor and a capacitor. The organic light emitting diode OLED includes a first electrode 552 , an intermediate layer 554 , and a second electrode 556 electrically connected to the pixel circuit 520 .

The intermediate layer 554 includes an organic light emitting layer, in addition to a hole transport layer (HTL), a hole injection layer (HIL), an electron transport layer (ETL), and an electron injection layer. : EIL) and the like may be further included.

The material of the substrate 510, the first electrode 552, and the second electrode 556 may be transparent, translucent, or transparent depending on the display direction of the display device 500, for example, bottom emission or top emission. Reflective materials may be used.

The encapsulation film EC is provided to protect the organic light emitting diode OLED and to improve the lifespan of the display device 500 . Although the encapsulation layer EC is illustrated as a single layer, this is exemplary and may be formed as a composite layer of a plurality of organic layers and inorganic layers.

The aforementioned inkjet printing method may be applied to manufacturing the display device 500 . After forming the display substrate 570 equipped with the organic light emitting diode (OLED), the display substrate 570 may be sealed with an encapsulation film EC. The organic layer and the inorganic layer constituting the encapsulation film EC may be manufactured according to a manufacturing method suitable for the material, and the inkjet printing method described above may be applied to at least one layer constituting the encapsulation film EC.

20 is a cross-sectional view showing another example of a display device to which an inkjet printing method according to an embodiment is applied.

The display device 600 includes a first substrate 610 on which a pixel circuit 614 for controlling a display area and a pixel electrode 616 are formed, and a second substrate 670 facing and spaced apart from the first substrate 610. , a liquid crystal layer LC positioned between the first substrate 610 and the second substrate 670 . The pixel circuit 520 may include a thin film transistor and a capacitor. The shape of the pixel electrode 616 is exemplary, and may have various patterns for controlling the liquid crystal layer LC.

To manufacture the display device 600, the above-described inkjet printing method may be used. A first substrate 610 having a pixel circuit 614 and a pixel electrode 616 is formed on the substrate 612, and the first alignment layer AL1 is formed on the first substrate 610 according to the inkjet printing method described above. ) can be formed.

In addition, a second substrate 670 having a color filter 674, a planarization layer 676, and a common electrode 678 is formed on the substrate 672, and a second alignment layer ( AL2) can be formed according to the inkjet printing method described above. It is exemplary that the color filter 674, the planarization layer 676, and the common electrode 678 are provided on the second substrate 670, and any one of the components may be provided on the first substrate 610. . Next, a liquid crystal layer LC is formed between the first substrate 610 and the second substrate 670 .

In the display devices 500 and 600 of FIGS. 19 and 20, as the inkjet printing method of the above-described embodiment is applied, the width of the film thickness deviation region near the edge of the print target region, that is, near the edge of the display device is Therefore, the display device 500 or 600 having a thin bezel can be manufactured.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

100: inkjet head
N1, N2, N3, N4, N5, N6: nozzles
LD: droplet
500, 600: display device
EC: Encapsulation
AL1, AL2: Alignment layer

Claims (20)

setting a first area to be printed at a constant print density in the area to be printed;
setting a second area to be printed with a printing density that varies depending on the location, as an area located at an edge of the print target area relative to the first area;
generating control data for a plurality of nozzles provided in an inkjet head to print the first area and the second area; and
driving the inkjet head according to the control data;
The control data, when the first area and the second area are divided into a plurality of unit areas facing the plurality of nozzles provided in the inkjet head, the interval or each volume of droplets to be ejected in the unit area data to control,
The generating of the control data includes selecting a printing density variable method for the second area,
When the droplet volume control type is selected as the printing density variable method for the second area, determining a ratio of the basic ejection amount of the droplets to be ejected to the plurality of unit areas of the second area; . According to claim 1,
The printing density of the second area is lower than the printing density of the first area. According to claim 2,
The inkjet printing method of claim 1 , wherein the printing density of the second area decreases toward the edge of the printing target area. delete According to claim 1,
Generating the control data
and setting a basic driving voltage that satisfies the tolerance range of the basic ejection amount for each of the plurality of nozzles provided in the inkjet head. According to claim 5,
Generating the control data
A basic driving voltage set for each of the plurality of nozzles is arranged in a row in a first direction in which the plurality of nozzles are arranged, and the row is arranged along a second direction in which the inkjet head moves relative to the print target area. An inkjet printing method comprising generating control data for printing the first area in the form of a repeated matrix. delete delete delete According to claim 1,
Generating the control data
The ratio determined for each of the plurality of unit areas of the second area and
The inkjet printing method of claim 1 , wherein control data for printing the second area is generated as data in a matrix form obtained by multiplying a plurality of nozzles facing each of the plurality of unit areas by a predetermined basic driving voltage. According to claim 1,
Generating the control data
When the print interval adjustment type is selected as the variable print density method,
The method of inkjet printing further comprising the step of determining a ratio of intervals between droplets to be jetted in the second area to intervals between droplets to be jetted in the first area. According to claim 11,
Generating the control data
Forming bitmap data in which a position where a liquid droplet is to be ejected is set to 1 and a position where a droplet is not to be ejected is set to 0 for the plurality of unit areas of the second area according to the spacing ratio; . According to claim 12,
the bitmap data determined for each of a plurality of unit areas of the second area;
The inkjet printing method of claim 1 , wherein control data for the second area is generated as data in a matrix form obtained by multiplying a basic driving voltage determined for each of a plurality of nozzles facing the plurality of unit areas. setting a first area to be printed at a constant print density in the area to be printed;
setting a second area to be printed with a printing density that varies depending on the location, as an area located at an edge of the print target area relative to the first area;
generating control data for a plurality of nozzles provided in an inkjet head to print the first area and the second area; and
driving the inkjet head according to the control data;
The control data, when the first area and the second area are divided into a plurality of unit areas facing the plurality of nozzles provided in the inkjet head, the interval or each volume of droplets to be ejected in the unit area data to control,
The generating of the control data includes selecting a printing density variable method for the second area,
When the mixed type of the droplet volume control type and the print interval control type is selected as the printing density variable method for the second area,
determining a ratio with respect to a basic discharge amount of droplets to be sprayed to a plurality of unit areas of the second area; and
The method of inkjet printing further comprising the step of determining a ratio of intervals between droplets to be jetted in the second area to intervals between droplets to be jetted in the first area. 15. The method of claim 14,
Generating the control data
Forming bitmap data in which a position where a liquid droplet is to be ejected is set to 1 and a position where a droplet is not to be ejected is set to 0 for the plurality of unit areas of the second area according to the spacing ratio; . According to claim 15,
Generating the control data
the bitmap data determined for each of a plurality of unit areas of the second area;
The ratio determined for each of the plurality of unit areas of the second area and
The inkjet printing method of claim 1 , wherein control data for printing the second area is generated as data in a matrix form obtained by multiplying a plurality of nozzles facing each of the plurality of unit areas by a predetermined basic driving voltage. forming a display substrate on which display elements are arrayed; and
Encapsulating the display substrate using an inkjet printing method; includes,
The inkjet printing method
setting a first area to be printed at a constant print density in the area to be printed;
setting a second area to be printed at a print density lower than that of the first area, as an area located at an edge of the print target area relative to the first area;
generating control data for a plurality of nozzles provided in an inkjet head to print the first area and the second area; and
driving an inkjet head according to the control data;
Wherein the generating of the control data includes determining a ratio to a basic discharge amount of liquid droplets to control a volume of the liquid droplets to be injected into the plurality of unit areas of the second area. According to claim 17,
The method of manufacturing a display device, wherein the display elements are organic light emitting elements. forming a first substrate on which pixel circuits and pixel electrodes for controlling a display area are formed; and
Forming a first alignment layer on the first substrate using an inkjet printing method;
The inkjet printing method
setting a first area to be printed at a constant print density in the area to be printed;
setting a second area to be printed at a print density lower than that of the first area, as an area located at an edge of the print target area relative to the first area;
generating control data for a plurality of nozzles provided in an inkjet head to print the first area and the second area; and
driving an inkjet head according to the control data;
Wherein the generating of the control data includes determining a ratio to a basic discharge amount of liquid droplets to control a volume of the liquid droplets to be injected into the plurality of unit areas of the second area. According to claim 19,
forming a second alignment layer on a second substrate using the inkjet printing method; and
Forming a liquid crystal layer between the first substrate and the second substrate; further comprising a display device manufacturing method.

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